Suppression of Epstein-Barr virus reactivation in lymphoblastoid cells cultured in simulated microgravity

Rotating-wall vessels allow for the growth of cells in simulated microgravity. Lymphoblastoid cells cultured in rotating-wall vessels exhibited significant differences in the expression of both early and late Epstein-Barr Virus (EBV) antigens. Viral protein expression (as measured by indirect immunofluorescence) was significantly suppressed in cells cultured in simulated microgravity. A significantly greater percentage of P3HR-1 cells and Daudi cells were positive for the expression of BamH1-Z-DNA fragment of Epstein-Barr replication activator (ZEBRA), early antigen restricted (EA-R), and viral capsid antigen (VCA) in cells cultured in static tissue culture flasks as compared to cells cultured in rotating-wall vessels. We observed a 7, 11, and 25-fold reduction, respectively, for EA-R, VCA, and ZEBRA protein in P3HR-1 cells cultured in simulated microgravity. Additionally, suspension cultures of P3HR-1 cells exhibited significantly greater ZEBRA antigen expression than cells cultured in rotating-wall vessels. As an independent confirmation of the reduction in ZEBRA-protein production in simulated microgravity in P3HR-1 cells, ZEBRA-mRNA was quantitated by reverse transcription polymerase chain reaction. We observed between a 4 to 10-fold reduction in ZEBRA-mRNA in cells cultured in simulated microgravity as compared to cells cultured at 1 x g in tissue culture flasks. Rotating-wall vessels, by virtue of providing a simple culture environment triggering marked differences in viral activation, provide a model whereby both host and viral factors involved in regulating the maintenance of EBV latency can be examined.